The present invention is directed to a process for the production of glass fiber light waveguides or conductors. The process involves chemical vapor deposition (CVD) and comprises forming glass layers on an inner surface of a rotating glass tube in a cycle which includes applying a layer of a substance from a flow of gas through the tube, subsequently transforming each applied layer of the substance into a glass layer, and then deforming or collapsing the internally coated glass tube into a rod from which a fiber is subsequently drawn.
An example of a process of a type in which a glass forming substance or glass substance is deposited on an inner surface of a tube and then transformed into a glass layer are generally known as a chemical vapor deposition (CVD) process. An example of such process is described in an article by P. Geittner et al, "Low-Loss Optical Fibers Prepared by Plasma-Activated Chemical Vapor Desposition (CVD)", Applied Physics Letter, Vol. 28, No. 11, June 1, 1976, pp. 645-6, and also in the articles mentioned in the footnotes 1-3 of this article. This tube is then formed into a rod and a fiber can then be drawn therefrom. A fiber which was formed by this process as well as fibers produced by a double crucible method have been proved to have the properties of being either depolarizing, birefringent, or optically active.
Practical applications for fibers, frequently required fibers which are neither depolarizing, birefringent nor optically active. For example, monomode glass fibers, which can be produced by a process as described above, would be predominantly suitable for the transmission of short light pulses in communication technology if the propagation delays between the two orthogonally polarized states of the fundamental mode in the fiber did not occur and thus undesireable reductions in the information transmission were not present in the fiber. Many other applications of the fiber will require a predetermined polarization of the emerging light. This occurs in interferometric processes such as a fiber optical rotation measurement process and in magneto-optical processes such as a fiber optical current strength meansurement process.
The origin of the undesireable properties of the real glass fibers includes deviations of the fiber core from the cylindrical symmetry or the anisotropy property of the material.